Wire feeders, like those used in arc welding applications, convey wire from a continuous feed source to a weld torch. In many instances, the wire is fed from a reel or drum at a rate determined by the operating parameters of the power source. Accordingly, the wire feeder includes a drive motor that delivers the wire at various feed rates. Typically pinch rollers are used to grip the wire pushing, or in certain cases pulling, it toward the work piece. To facilitate smooth operation, bearings may be included that allow the pinch rollers to rotate with reduced friction.
However, it is known that using aluminum as a welding wire is increasing due to its lightweight attributes and corrosion-resistant properties. However, aluminum can present some real challenges. Equipment must be adapted specifically to handle the softer aluminum wire and machine settings that work well with steel wire may not be appropriate. In fact, aluminum wire can easily be damaged by equipment set up for steel wire.
One of the recommended changes is the use of a nylon or Teflon® liner to reduce friction and wire shaving. It is also recommended to substitute a U-shaped groove in the drive rolls, rather than a more traditional V-shaped groove so that there are no sharp edges to shave off the aluminum wire. Also, the tension on the drive roll should be reduced from typical steel settings to prevent crushing the aluminum wire during feeding. Since aluminum expands more than steel as it heats up, the proper-sized hole in the contact thip is larger for aluminum than for steel. Brake tension on the wire spindle should be set more loosely than it would normally be set for steel so that less force is required to pull the wire off the spool.
Because the column strength of aluminum is much less than steel, feeding aluminum wire often requires special feed mechanisms. One way to assist in the feeding of aluminum wire is to use a “push-pull” system which utilizes dual motors: an assist motor that pushes the electrode from the feeder and a primary motor that is located in the gun that pulls the electrode. This type of system offers superior feeding performance of a spool gun with many of the advantages of a compact push system. A push-pull system provides the most uniform feeding and can hold larger spools of wire. The gun can be taken long distances from the power source and does not require the costly 1 lb. spools of the spool gun method and has a comfortable ergonomic gun that fits into tighter places.